fix: align search field focus across five bindings

[yunfeizhu]

Closes #346.

Changes

• Align the title-bar and File > Open/Recent search fields across React, Vue, Angular, Svelte, and Vanilla with a single restrained focus border, consistent icon alignment, and a shared style contract where possible.
• Keep keyboard focus visible in forced-colors mode without drawing a second outline on the inner input.
• Preserve focus in the Vanilla recent-files search while filtering and loading results.

Verification

• Full workspace build passed.
• Search-field browser tests passed across all five demos (15 tests), covering focus, forced colors, and an 800px viewport.
• Pre-commit formatting and lint checks passed.

[github-actions]

Cross-binding parity check

This is advisory only and does not block the PR. It looks at changed file paths, so it cannot tell a genuinely framework-specific change from a parity gap. If it is wrong here, just say so in a comment.

Binding	This PR
React	changed
Vue	changed
Angular	changed
Svelte	changed
Vanilla	changed

Some changed bindings have no test changes

No test files changed under: React, Vue, Angular, Svelte, Vanilla.

---

See the parity rule for what is expected. Missing: none.

[yunfeizhu]

@ChristopherVR Could you please rerun the failed jobs for this PR?

The React E2E shard 3/8 was cancelled at the 25-minute job limit after the GIF Default Resolution parity test hit its 240-second test timeout twice. ci-success failed because that shard was cancelled. The same test also hit the 240-second timeout on its first attempt in a main CI run, then passed on retry in 2.8 minutes. This looks like existing timing variability rather than a search-field regression. I tried rerunning the failed jobs, but GitHub requires repository admin permission for that action.